Calling Prolog from Java

A Prolog call is an instance of the class bprolog.plc.Plc. It is convenient to import the class first:

       import bprolog.plc.Plc;

The class Plc contains the following constructor and methods:

• public Plc(String functor, Object args[]) It constructs a prolog call where functor is the predicate name, and args is the sequence of arguments of the call. If a call does not carry any argument, then just give the second arguemnt an empty array new Object[] .

• public static void startPlc(String args[]) Initialize the B-Prolog emulator, where args are parameter-value pairs given to B-Prolog. Possible parameter-value pairs include:

  
  		  "-b" TRAIL : words allocated to the trail stack 
  
  		  "-s" STACK : words allocated to the local and the heap 
  
  		  "-p" PAREA : words allocated to the program code area 
  
  		  "-t" TABLE : words allocated to the table area
  

  where TRAIL, STACK, PAREA and TABLE must all be strings of integers. After the B-Prolog emulator is initialized, it will be waiting for calls from Java. Initialization needs to be done only once. Further calls to startPlc have no effect at all.

• public static native boolean exec(String command) Execute a Prolog call as represented by the string command. This method is static, and thus can be executed without creating any Plc object. To call a predicate in a file, say xxx.pl, it is necessary to first have the Prolog program loaded into the system. To do so, just execute the method exec("load(xxx)") or exec("consult(xxx)".

• public boolean call() Execute the Prolog call as represented by the Plc object that owns this method. The return value is true if the Prolog call succeeds or false if the call fails.